Carbometalation of alkynylsilanes with 1/1 titanocene dichloride/dialkylaluminum chloride is stereospecifically cis. The alkenyltitanium intermediate can be stereospecifically protonated by aqueous sodium hydroxide or iodinated. Addition of any Lewis base to the alkenyltitanium intermediate induces decomposition of this intermediate to give an alkene by hydrogen atom abstraction from the medium, with loss of stereochemistry.
38. Snider, B. B.; Roush, D. M.; Killinger, T. A. “Intramolecular Reactions of 1-Allylic 2,2-Dimethyl Ethylenetricarboxylates” J. Am. Chem. Soc. 1979, 101, 6023-6027. http://dx.doi.org/10.1021/ja00514a026
1-Allylic 2,2-dimethyl ethylenetricarboxylates undergo intramolecular cyclization reactions at 80-140 °C giving mixtures of ene adducts and dihydropyrans in which the α,β-unsaturated ester functions as diene in an inverse electron demand Diels-Alder reaction. The trans-crotyl trimester 6 reacts at I35 °C giving a 1:1 mixture of the cis-substituted ene adduct 8 and the Diels-Alder adduct 7. The ene adducts are of value as a-methylene lactone precursors while the pyrans will be of value in synthesis of iridoids and their analogues.
37. Snider, B. B.; Van Straten, J. W. “Stereochemistry of Ene Reactions of Glyoxylate Esters” J. Org. Chem. 1979, 44, 3567-3571. http://dx.doi.org/10.1021/jo01334a025
The stereochemistry of the thermal and catalytic ene reactions of methyl glyoxylate is examined. With cis-2-butene at 200 ºC, a 54% yield of a 7.4:1 mixture of endo-exo adducts is obtained. With cyclohexene and ferric chloride catalyst, a 4.4:1 mixture of endo-exo adducts is obtained.
36. Snider, B. B.; Conn, R. S. E.; Karras, M. “Nickel-Catalyzed Carbometalation of Functionalized Silylalkynes by Grignard Reagents” Tetrahedron Lett. 1979, 1679-1682. http://dx.doi.org/10.1016/S0040-4039(01)93622-6
Syntheses of vinylsilanes by the nickel catalyzed addition of methyl-magnesium bromide to functionalized silylalkynes are described. Simple syntheses of geraniol and farnesol are reported.
35. Snider, B. B.; Roush, D. M. “Lewis Acid Induced Cyclizations of Ethylenetricarboxylates” J. Org. Chem. 1979, 44, 4229-4232. http://dx.doi.org/10.1021/jo01338a003
34. Snider, B. B.; Rodini, D. J.; Conn, R. S. E.; Sealfon, S. “Lewis Acid Catalyzed Reactions of Methyl Propiolate with Unactivated Alkenes” J. Am. Chem. Soc. 1979, 101, 5283-5293. http://dx.doi.org/10.1021/ja00512a029
Methyl propiolate undergoes Lewis acid catalyzed reactions with alkenes in high yield. mono- and 1,2-disubstituted alkenes give mainly cyclobutenes. 1 ,I-Disubstituted, trisubstituted, and tetrasubstitutecl alkenes give only ene adducts. Use of ethylaluminum dichloride as catalyst allows the isolation of pure products from acid-sensitive alkenes. Functionalized alkenes containing nonbasic functional groups are suitable substrates. Alkenes containing more basic functional groups are suitable if 2 equiv of catalyst is used.
33. Snider, B. B.; Roush, D. M. “Aluminum Chloride Catalyzed Reactions of Methyl Chloropropiolate with Unactivated Alkenes” J. Am. Chem. Soc. 1979, 101, 1906-1907. http://dx.doi.org/10.1021/ja00501a059
32. Snider, B. B.; Conn, R. S. E.; Sealfon, S. “Reactions of Phenylhydrazones with Electron-Deficient Alkenes” J. Org. Chem. 1979, 44, 218-221. http://dx.doi.org/10.1021/jo01316a012
Reaction of aliphatic aldehyde phenylhydrazones with methyl acrylate or acrylonitrile gives phenylazoalkanes by an ene reaction. With more electron-deficient alkenes such as methyl vinyl ketone or /3-nitrostyrene, Michael reaction at nitrogen occurs followed by cyclization to give pyrazolidines.
31. Snider, B. B.; Karras, M.; Conn, R. S. E. “Nickel-Catalyzed Addition of Grignard Reagents to Silylacetylenes. Synthesis of Tetrasubstituted Alkenes” J. Am. Chem. Soc. 1978, 100, 4624-4626. http://dx.doi.org/10.1021/ja00482a066
30. Snider, B. B.; Rodini, D. “Synthesis of the A1 Component of the Female Sex Pheromone of the California Red Scale” Tetrahedron Lett. 1978, 1399-1400. http://dx.doi.org/10.1016/S0040-4039(01)94555-1
29. Snider, B. B.; Amin, S. G. “A Synthetic Precursor of Verrucarin” Synth. Commun. 1978, 8, 117-125. http://dx.doi.org/10.1080/00397917808062105
28. Snider, B. B.; Killinger, T. A. “Rate Acceleration of the Intramolecular Ene Reactions of 1,6- and 1,7-Enynes by Electron-Withdrawing Substituents.” J. Org. Chem. 1978, 43, 2161-2164. http://dx.doi.org/10.1021/jo00405a016
The intramolecular ene reactions of 1,6- and 1,7-enynes containing a hydrogen, methyl, or carbomethoxy substituent of the acetylene have been investigated. Since the acetylene is acting as the enophile, the methyl substituent retards the reaction while the carbomethoxy group significantly accelerates it. A terminal 1,6-enyne, 1, cyclizes at 210 °C while the carbomethoxy enyne 2 cyclizes at 135 °C.
27. Snider, B. B.; Fuzesi, L. “Allylic Functionalization: the Preparation of Allylmalonates” Tetrahedron Lett. 1978, 877-880. http://dx.doi.org/10.1016/S0040-4039(01)91424-8